Log in to the client as admin and you will already see a group created for duplicate accounts called: Duplicate Suspects
If you dont have it..? Here is how to create it:
Create a Group on the Account field using the In Operator and add the following SQL within the Value Is box:
SELECT ACCOUNT FROM ACCOUNT WHERE ACCOUNTID <> 'NOTHING' GROUP BY ACCOUNT HAVING COUNT(*) > 1
You must also check the Option for Use Value as Literal
Regards, Adam Travers